Purification of long chain diacids

ABSTRACT

The present disclosure relates to methods for separating and purifying a long chain diacid from other long chain diacids, monocarboxylic acids, hydroxyl acids or alkanes by simulated or actual moving bed chromatography.

RELATED APPLICATIONS

This application claims priority from U.S. Provisional application Ser.Nos. 62/044,822, filed Sep. 2, 2015 and 62/194,024, filed Jul. 17, 2015,the entire contents of which are incorporated by reference herein intheir entirety.

FIELD OF THE INVENTION

The invention relates to methods for separating and purifying a longchain diacid from other long chain diacids, monocarboxylic acids,hydroxyl acids or alkanes by simulated or actual moving bedchromatography.

BACKGROUND OF THE TECHNOLOGY

Dicarboxylic acids comprising six or more carbon atoms are commonlyreferred to as “long-chain diacids”. Long-chain diacids can be used asbasic constituent monomer for a series of synthetic materials. Potentialuses of long-chain diacids and their derivatives include, for example,production of special nylon resins, polycarbonate, powder coatings,fragrances, hot-melt adhesives and special lubricants. Long-chaindiacids can also be used as plasticizers for engineering plastics andcorrosion inhibitors in, for example, metal processing technology. Whenused as constituent monomers for production of special nylon, long-chaindiacids can demonstrate some unique performance characteristics whencompared to other monomers.

Commercial quantities of long-chain diacids are generally not found innature. Certain long-chain diacids, for example adipic acid, sebacicacid and dodecanedioic acid, can be prepared via chemical methods. Forexample, starting with benzene or 1,3-butadiene, dodecanedioic acid canbe prepared through multiple steps of chemical reactions. Sebacic acidcan be prepared through the chemical conversion of castor oil. Startingwith cyclohexane, adipic acid can be prepared through multiple steps ofoxidation. Long-chain diacids can also be prepared via a biologicalmethod. A biological method, for example fermentation, can produce aseries of long-chain diacids containing 6 through 18 carbon atoms. Someof the chemical and biological routes to diacids can result in lowlevels of analogous chain length monocarboxylic acids and/or hydroxylacids as impurities. As these impurities can impact the suitability ofthe diacids in the desired applications, removal of the monocarboxylicacid and hydroxyl acid from the diacid is critical.

Chromatography, for example paper chromatography, gas chromatography,and high pressure liquid chromatography, can be utilized foridentification and separation of long-chain diacids. The targetlong-chain diacid(s) and impurities have different interacting forceswith the chromatograph stationary phase. Under specific elutingconditions and/or with a specific chromatograph stationary phase, thedifferences between the interacting forces could be large enough toachieve separation of different components. US20120253069 describes alaboratory method of using liquid chromatography with a packed bedcolumn to separate long chain diacids from alkanes and other long chainsdiacids.

The process of separating a binary mixture is illustrated with referenceto a single zone system as shown in FIG. 1. The concept of a simulatedor actual continuous countercurrent chromatographic separation processis explained by considering a vertical chromatographic column containingstationary phase S divided into sections, more precisely into foursuperimposed sub-zones I, II, III and IV going from the bottom to thetop of the column. The eluent is introduced at the bottom at IE by meansof a pump P. The mixture of the components A and B which are to beseparated is introduced at IA+B between sub-zone II and sub-zone III. Anextract containing mainly B is collected at SB between sub-zone I andsub-zone II, and a raffinate containing mainly A is collected at SAbetween sub-zone III and sub-zone IV.

In the case of a simulated moving bed system, a simulated downwardmovement of the stationary phase S is caused by movement of theintroduction and collection points relative to the solid phase. In thecase of an actual moving bed system, downward movement of the stationaryphase S is caused by movement of the various chromatographic columnsrelative to the introduction and collection points. In FIG. 1, eluentflows upward and mixture A+B is injected between sub-zone II andsub-zone III. The components will move according to theirchromatographic interactions with the stationary phase, for exampleadsorption on a porous medium. The component B that exhibits strongeraffinity to the stationary phase (the slower running component) will bemore slowly entrained by the eluent and will follow it with delay. Thecomponent A that exhibits the weaker affinity to the stationary phase(the faster running component) will be easily entrained by the eluent.If the right set of parameters, especially the flow rate in each zone,are correctly estimated and controlled, the component A exhibiting theweaker affinity to the stationary phase will be collected betweensubzone III and sub-zone IV as a raffinate and the component Bexhibiting the stronger affinity to the stationary phase will becollected between sub-zone I and sub-zone II as an extract.

SUMMARY OF THE INVENTION

There is a desire in industry to separate and purify long-chain diacidsproduced in a commercial scale biological process in a simple andlow-cost way, but this is challenging because of the similar structuresbetween impurity acids and the target products. For example, when analkane is used as substrate to produce long-chain diacids viafermentation, a mixture of diacids with different chain lengths,monocarboxylic acids and hydroxyl acids could be produced. This complexmixture of diacids is due, in part, to the alkanes having differentchain length serving as the fermentation raw material and/or due todifferent metabolic pathways in the microorganism used to perform thefermentation. Also, for example, when fatty acid and/or its derivativesare used as the fermentation raw material, small quantities of fattyacid and its derivatives may remain in the fermentation product broth.

Commercial applications of long-chain diacids may require them to be ofvery high purity with low quantities of color-inducing impurities andhigh heat stability. Long-chain diacids that are the basic constituentmonomer for commercial nylons (e.g., polyamides) may need to have verylow monocarboxylic acid content or hydroxyl acid content, because suchimpurities can terminate the polymerization, leading to lower molecularweight polymers, and/or cap the terminal amine of the polymer, leadingto lower dyeability. The content of color-inducing impurities that mayreact under high temperature may also need to be very low because it mayaffect the color and performance of nylon.

Examples of long-chain diacids contemplated for the methods disclosedherein are polymer grade dodecanedioic acid (for example for Nylon 6,12or Nylon 12,12), polymer grade sebacic acid (for example for Nylon 5,10or Nylon 6,10), and polymer grade adipic acid (for example for Nylon6,6). For these polymer-grade long-chain diacids, it is typical forimpurities such as monocarboxylic acid and hydroxyl acid to be at verylow content, such as in the parts per million weight (ppmw) range, suchas 10,000 ppmw or less, such as 5,000 ppmw or less, such as 1,000 ppmwor less, such as 500 ppmw or less, such as 100 ppmw or less, such as 50ppmw or less, or such as 10 ppmw or less. As another example, tocomprise an ingredient in the fragrance Musk-T, tridecanedioic acid musthave low impurity levels, because impurities, including different acids,can affect the fragrance of Musk-T. Therefore, it is desirable todevelop commercially suitable methods for the separation and purifying along chain diacid from other long chain diacids, monocarboxylic acids,hydroxyl acids or alkanes.

The method of the present invention allows for large scale commercialproduction of high purity of long chain diacid product, for example byavoiding the problems of cost associated with recrystallization of longchain diacids. The quantity of isomeric impurities present in a longchain diacid product of the present invention will depend on the amountof impurities or additional undesired long chain diacids present in thefeed mixture. The invention disclosed herein provides commerciallysuitable methods for the separation and purifying a long chain diacidfrom other long chain diacids, monocarboxylic acids, hydroxyl acids oralkanes by simulated moving bed chromatography. The long chain diacidproduct can comprise at least one long-chain diacid comprising an α,ω-aliphatic diacid with the main chain comprising 6 or more carbonatoms, or comprising 8 or more carbon atoms, for example, alkane diacidsand olefin diacids comprising from 6 to 18 carbons. For example, thelong chain diacid can be C6 diacid (adipic acid), C7 diacid (pimelicacid), C8 diacid (suberic), C9 diacid (azelaic acid), C10 diacid(sebacic acid), C11 diacid (undecanedioic acid), C12 diacid(dodecanedioic acid), C13 diacid (tridecanedioic acid), C14 diacid(tetradecanedioic acid), C15 diacid (pentadecanedioic acid), C16 diacid(hexadecanedioic acid), C17 diacid, (heptadecanedioic acid) C18 diacid(octadecanedioic acid), or C6-18-olefin diacid. In some aspects, the atleast one long-chain diacid can be one single long-chain diacid, or amixture of different long-chain diacids. In one aspect, the long chaindiacid product can be adipic acid, sebacic acid or dodecanedioic acid.In another aspect, the long chain diacid product can be produced viachemical methods. In yet another aspect, the long chain diacid isproduced by fermentation of long chain alkanes, fatty acids, or fattyacid esters.

In one aspect, the hydroxyl acid impurities can be ω-hydroxyacids suchas ω-hydroxycaproic acid in the C-6 adipic acid case, ω-hydroxydecanoicacid in the C-10 sebacic acid case, and/or ω-hydroxydodecanoic acid inthe C-12 dodecanedioic acid acid case.

In one aspect, the method of the present invention comprises a pluralityof separation zones. In another aspect, two or more separation zones areused. In yet another aspect, there are 2 to 5 separation zones.Typically, the components separated in each zone have differentpolarities. Each zone contains an eluent, for example an aqueousalcohol, comprising various water:alcohol ratios, and/or a recyclestream comprising the extract and/or raffinate streams recycled backinto the same zone. The eluent and/or recycle stream can be adjustedsuch that the long chain diacid product can be separated from differentcomponents of the feed mixture in each zone.

In another aspect, the present invention relates to compositionscomprising a long chain diacid product, for example one obtainable bythe method of the present invention.

In one aspect, this disclosure features a method for separating a LCDA(e.g., a C6- to C18-carbon diacid) from at least one impurity in asolution, the method comprising (a) introducing a feed stream comprisinga solution comprising at least one 6- to 18-carbon diacid and at leastone impurity, the at least one impurity comprising a component morepolar than the diacid, a component less polar than the diacid, or both,into a first zone of moving bed chromatography apparatus (MBCA) havingone or more zones, (b) collecting a raffinate stream or an extractstream from the first zone of the MBCA, the raffinate stream comprisingthe diacid and components more polar than the diacid, and the extractstream comprising the diacid and components less polar than the diacid,(c) introducing the raffinate stream or the extract stream into a secondzone of the MBCA, (d) collecting a second raffinate stream or a secondextract stream from the second zone of the MBCA, the raffinate streamcomprising the diacid and components more polar than the diacid, and theextract stream comprising the diacid and components less polar than thediacid, (e) introducing the second raffinate stream or the secondextract stream into the first zone or the second zone of the MBCA, (f)optionally repeating steps (d) and (e) until a desired degree ofseparation is achieved; and (g) collecting a final raffinate stream or afinal extract stream from a zone the MBCA, the final raffinate stream orthe extract stream comprising the diacid, thereby separating a C6- toC18-carbon diacid from the at least one impurity in the solution.

This disclosure also features method for separating a C6- to C18-carbondiacid from at least one impurity in a solution, the method comprising(a) introducing a feed stream comprising a solution comprising at leastone 6- to 18-carbon diacid and at least one impurity, the at least oneimpurity comprising a component more polar than the diacid, a componentless polar than the diacid, or both, into a first zone of a moving bedchromatography apparatus (MBCA), (b) collecting a raffinate stream or anextract stream from the MBCA, the raffinate stream comprising the diacidand components more polar than the diacid, and the extract streamcomprising the diacid and components less polar than the diacid, (c)introducing the raffinate stream or the extract stream into the firstzone of the MBCA, (f) optionally repeating steps (b) and (c) until adesired degree of separation is achieved; and (g) collecting a finalraffinate stream or a final extract stream from the first zone of theMBCA, the final raffinate stream or the extract stream comprising thediacid, thereby separating a C6- to C18-carbon diacid from the solution.

In another aspect, this disclosure features moving bed chromatographyapparatus (MBCA) for separating a C6- to C18-carbon diacid from at leastone impurity in a solution, the MBCA comprising a first zone configuredto receive a feed stream comprising a solution comprising at least one6- to 18-carbon diacid and at least one impurity, the at least oneimpurity comprising a component more polar than the diacid, a componentless polar than the diacid, or both, (b) the first zone configured toproduce a raffinate stream or an extract stream from the MBCA, theraffinate stream comprising the diacid and components more polar thanthe diacid, and the extract stream comprising the diacid and componentsless polar than the diacid, (c) a second zone configured to receive theraffinate stream or the extract stream produced from the first zone, (d)the second zone configured to produce a raffinate stream or an extractstream from the MBCA, the raffinate stream comprising the diacid andcomponents more polar than the diacid, and the extract stream comprisingthe diacid and components less polar than the diacid, (e) the MBCAconfigured to allow repeating steps (d) and (e) until a desired degreeof separation is achieved to produce a final raffinate stream or a finalextract stream from a zone the MBCA, the final raffinate stream or theextract stream comprising the diacid, thereby separating a C6- toC18-carbon diacid from the solution.

In some aspects, the methods and apparatus disclosed herein optionallycomprising introducing the raffinate stream or the extract stream intofirst zone of the MBCA prior to first raffinate stream or the firstextract stream introducing the raffinate stream or the extract streaminto a second zone of the MBCA. In some embodiments, the MBCA comprisestwo or more zones, each zone comprising one or more injection points forintroducing the solution; one or more injection points for introducingan eluent; a raffinate stream from which liquid can be collected; and anextract stream from which liquid can be collected.

In some embodiments, the at least one impurity is present in a finalraffinate stream or a final extract stream at about 10,000 ppmw or less,about 5,000 ppmw or less, about 1,000 ppmw or less, about 500 ppmw orless, about 100 ppmw or less, about 50 ppmw or less, or about 10 ppmw orless. The at least one impurity can be a monocarboxylic acid, an alkane,or a hydroxyl acid. The at least one impurity can be more polar than theLCDA, or can be less polar than LCDA.

According to some aspects, the C6- to C18-carbon diacid recovered fromthe methods and apparatus disclosed herein is at least 80%, 82%, 85%,88%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or at least 99.9%relative to the amount of the at least one impurity.

In some embodiments, the at least one 6- to 18-carbon diacid is an, ordiacid, including, for example a alkane diacid or an olefin diacid. The6- to 18-carbon diacid can be produced by chemical means or byfermentation. Thus, in some embodiments, the 6- to 18-carbon diacid is abioderived compound produced by fermentation.

The at least one 6- to 18-carbon diacid can be, for example, a LCDAselected from the group consisting of a C6 diacid (adipic acid), C7diacid (pimelic acid), C8 diacid (suberic), C9 diacid (azelaic acid),C10 diacid (sebacic acid), C11 diacid (undecanedioic acid), C12 diacid(dodecanedioic acid), C13 diacid (tridecanedioic acid), C14 diacid(tetradecanedioic acid), C15 diacid (pentadecanedioic acid), C16 diacid(hexadecanedioic acid), C17 diacid, (heptadecanedioic acid) C18 diacid(octadecanedioic acid), and C6-18-olefin diacid.

According to some aspects, the MBCA comprises one, two or more zones.The MBCA can contain one, two, three to fifteen chromatography columns.

In some embodiments, the apparatus comprises two zones, the eluent inthe first zone containing more alcohol than the eluent in the secondzone, and the second zone is downstream of the first zone with respectto the flow of eluent in the system.

In some embodiments, the apparatus comprises a first zone, a second zoneand a third zone, the eluent in the first zone containing more alcoholthan the eluent in the second zone and the third zone and the first zoneis upstream of the second and third zones with respect to the flow ofeluent in the system, and the eluent in the second zone contains morealcohol than the eluent in the third zone and the second zone isupstream of the third zone with respect to the flow of eluent in thesystem.

In some aspects, this disclosure provides a method, means or process forobtaining a diacid comprising providing a solution comprising at leastone C6- to C18-carbon diacid and at least one impurity; introducing thesolution into a moving bed chromatography apparatus (MBCA) having one ormore chromatography columns and at least one eluent; producing araffinate and an extract; recovering a purified C6- to C18-carbon diacidcomposition from the raffinate or the extract, or both, wherein said atleast one impurity is present in the purified diacid composition atabout 10,000 ppmw or less, about 5,000 ppmw or less, about 1,000 ppmw orless, about 500 ppmw or less, about 100 ppmw or less, about 50 ppmw orless, or about 10 ppmw or less.

In an exemplary embodiment, the disclosure provides a method forseparating adipic acid from 6-hydroxycaproic acid and caproic acid in asolution, the method comprising (a) introducing a feed stream comprisinga solution comprising adipic acid, 6-hydroxycaproic acid, and caproicacid, into a first zone of moving bed chromatography apparatus (MBCA);(b) collecting a raffinate stream or an extract stream from the firstzone of the MBCA, the raffinate stream comprising the adipic acid and6-hydroxycaproic acid, and the extract stream comprising the adipic acidand caproic acid; (c) introducing the raffinate stream or the extractstream into a second zone of the MBCA; (d) collecting a second raffinatestream or a second extract stream from the second zone of the MBCA, theraffinate stream comprising the adipic acid and 6-hydroxycaproic acid,and the extract stream comprising the adipic acid and caproic acid; (e)introducing the second raffinate stream or the second extract streaminto the first zone or the second zone of the MBCA; (f) optionallyrepeating steps (d) and (e) until a desired degree of separation isachieved; and (g) collecting a final raffinate stream or a final extractstream from a zone of the MBCA, the final raffinate stream or theextract stream comprising the adipic acid, thereby separating the adipicacid from the 6-hydroxycaproic acid and caproic acid.

In another exemplary embodiment, the disclosure provides method forseparating dodecandioic acid from 12-hydroxydecanoic acid and lauricacid in a solution, the method comprising: (a) introducing a feed streamcomprising a solution comprising dodecandioic acid, 12-hydroxydecanoicacid and lauric acid, into a first zone of moving bed chromatographyapparatus (MBCA); (b) collecting a raffinate stream or an extract streamfrom the first zone of the MBCA, the raffinate stream comprising thedodecandioic acid and 12-hydroxydecanoic acid, and the extract streamcomprising the dodecandioic acid and lauric acid; (c) introducing theraffinate stream or the extract stream into a second zone of the MBCA;(d) collecting a second raffinate stream or a second extract stream fromthe second zone of the MBCA, the raffinate stream comprising thedodecandioic acid and 12-hydroxydecanoic acid, and the extract streamcomprising the dodecandioic acid and lauric acid; (e) introducing thesecond raffinate stream or the second extract stream into the first zoneor the second zone of the MBCA; (f) optionally repeating steps (d) and(e) until a desired degree of separation is achieved; and (g) collectinga final raffinate stream or a final extract stream from a zone of theMBCA, the final raffinate stream or the extract stream comprising thedodecandioic acid, thereby separating the dodecandioic acid from the12-hydroxydecanoic acid and lauric acid.

Definitions

While mostly familiar to those versed in the art, the followingdefinitions are provided in the interest of clarity.

“Zone” refers to a plurality of linked chromatography columnscontaining, as eluent (i.e. an aqueous alcohol) and having one or moreinjection points for a feed mixture stream, one or more injection pointsfor water and/or alcohol, a raffinate take-off stream from which liquidcan be collected from said plurality of linked chromatography columns,and an extract take-off stream from which liquid can be collected fromsaid plurality of linked chromatography columns. Typically, each zonehas only one injection point for a feed mixture. In one aspect, eachzone has only one injection point for the eluent. In another aspect,each zone has two or more injection points for water and/or alcohol.

“Raffinate” is the stream of components that move more rapidly with theliquid eluent phase compared with the solid adsorbent phase. Thus, araffinate stream can be enriched with more polar components, anddepleted of less polar components compared with a feed stream.

“Extract” is the stream of components that move more rapidly with thesolid adsorbent phase compared with the liquid eluent phase. Thus, anextract stream can be enriched with less polar components, and depletedof more polar components compared with a feed stream.

“Nonadjacent” when applied to columns in the same apparatus refers tocolumns separated by one or more columns, for example 3 or more columns,for example 5 or more columns, or for example about 5 columns.

“LCDA” means long chain diacid(s).

“MB” means moving bed chromatography. “MBCA” means moving bedchromatography apparatus.

“SMB” means simulated moving bed chromatography.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the basic principles of a simulated or actual movingbed process for separating a binary mixture.

FIG. 2 illustrates a first aspect of the invention which is suitable forseparating desired LCDA from faster and slower running components (i.e.more polar and less polar impurities).

FIG. 3 illustrates a second aspect of the invention which is suitablefor separating desired LCDA from faster and slower running components(i.e. more polar and less polar impurities).

FIG. 4 illustrates in more detail the first aspect of the inventionwhich is suitable for separating desired LCDA from faster and slowerrunning components (i.e. more polar and less polar impurities).

FIG. 5 illustrates in more detail the second aspect of the inventionwhich is suitable for separating desired LCDA from faster and slowerrunning components (i.e. more polar and less polar impurities).

FIG. 6 illustrates in more detail an alternative method for the firstaspect of the invention which is suitable for separating desired LCDAfrom faster and slower running components (i.e. more polar and lesspolar impurities).

FIG. 7 illustrates in more detail an alternative method for the secondaspect of the invention which is suitable for separating desired LCDAfrom faster and slower running components (i.e. more polar and lesspolar impurities).

FIG. 8 illustrates an aspect of the invention for purifying desired LCDAfrom faster and slower running components (i.e. more polar and lesspolar impurities).

FIG. 9 illustrates an alternative method for an aspect of the inventionfor purifying desired LCDA from faster and slower running components(i.e. more polar and less polar impurities).

FIG. 10 illustrates an aspect of the invention for purifying desiredLCDA from faster and slower running components (i.e. more polar and lesspolar impurities).

FIG. 11 illustrates an adsorption pulse test for a feed mixturecomprising a C6 diacid.

FIG. 12 illustrates an adsorption pulse test for a feed mixturecomprising a C6 diacid.

FIG. 13 illustrates an adsorption pulse test for a feed mixturecomprising a C12 diacid.

DETAILED DESCRIPTION OF THE INVENTION

The method of the present invention comprises the separation andpurification at least one long chain diacid from other long chaindiacids, monocarboxylic acids, hydroxyl acids or alkanes in a solutionby simulated moving bed chromatography. The long chain diacid cancomprise at least one long-chain diacid comprising an α, ω-aliphaticdiacid with the main chain comprising 6 or more carbon atoms, forexample, alkane diacids and olefin diacids comprising from 6 to 18carbons. For example, the long chain diacid can be C6 diacid (adipicacid), C7 diacid (pimelic acid), C8 diacid (suberic), C9 diacid (azelaicacid), C10 diacid (sebacic acid), CI 1 diacid (undecanedioic acid), C12diacid (dodecanedioic acid), C13 diacid (tridecanedioic acid), C14diacid (tetradecanedioic acid), C15 diacid (pentadecanedioic acid), C16diacid (hexadecanedioic acid), C17 diacid, (heptadecanedioic acid) C18diacid (octadecanedioic acid), or C18-9-olefin diacid. In some aspects,the at least one long-chain diacid can be one single long-chain diacid,or a mixture of different long-chain diacids. In one aspect, the longchain diacid product can be adipic acid, sebacic acid or dodecanedioicacid. In another aspect, the long chain diacid product can be producedvia chemical methods. In yet another aspect, the long chain diacid isproduced by fermentation routes. In another aspect, the fermentationroute comprises fermentation of long chain alkanes, fatty acids, orfatty acid esters.

In one aspect, the method of the present invention comprises introducinga feed stream comprising at least one long chain diacid in to a movingbed chromatography apparatus (MBCA). The MBCA can contain a plurality ofseparation zones. For example, the MBCA can contain one, two or moreseparation zones. In yet another aspect, the MBCA can contains 2 to 5separation zones. Typically, the components separated in each zone havedifferent polarities. Each zone contains an eluent, for example anaqueous alcohol, comprising various water:alcohol ratios, and/or arecycle stream comprising the extract and/or raffinate streams recycledback into the same zone. The eluent and/or recycle stream can beadjusted such that the long chain diacid product can be separated fromdifferent components of the feed mixture in each zone.

In another aspect, the present invention relates to compositionscomprising a long chain diacid product, for example a long chain diacidproduct obtainable by the method of the present invention. Thecomposition comprising a long chain diacid product comprise at least80%, 82%, 85%, 88%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%,99.5% or at least 99.9% of the long chain diacid product relative to theamount of any other long chain diacids, monocarboxylic acids, hydroxylacids or alkanes in the composition.

Suitable feed mixtures for fractionating by the method of the presentinvention can be obtained by chemical and/or biological methods. Certainlong-chain diacids, for example adipic acid, sebacic acid anddodecanedioic acid, can be prepared via chemical methods. For example,starting with benzene or 1,3-butadiene, dodecanedioic acid can beprepared through multiple steps of chemical reactions. Sebacic acid canbe prepared through the chemical conversion of castor oil. Long-chaindiacids can also be prepared via a biological method. A biologicalmethod, for example fermentation, can produce a series of long-chaindiacids containing 6 through 18 carbon atoms.

The feed mixtures can contain the desired LCDA product and at least onemore polar component or at least one less polar component. The lesspolar components can have a stronger adherence to the adsorbent used inthe method of the present invention as compared to the desired LCDAproduct. During operation, such less polar components typically movewith the solid adsorbent phase in preference to the liquid eluent phase.The more polar components have a weaker adherence to the adsorbent usedin the method of the present invention than does the LCDA product.During operation, such more polar components typically move with theliquid eluent phase in preference to the solid adsorbent phase. Ingeneral, more polar components will be separated into a raffinatestream, and less polar components will be separated into an extractstream.

Examples of the more and less polar components include (1) othercompounds from the manufacturing process (for example, other unwantedLCDAs, hydroxylated fatty acids, fatty acids, fatty acid esters,hydrocarbons, or hydroxycarboxylic acids), (2) byproducts formed duringstorage, refining and previous concentration steps and (3) contaminantsfrom solvents or reagents which are utilized during previousconcentration or purification steps.

In one aspect, the feed mixture is a LCDA containing mainly the desiredLCDA.

In one aspect, the feed mixture is an aqueous mixture containing theLCDA, such as a fermentation broth from a biological fermentation.

MBCAs suitable for the separation and purifying a LCDA from a feedmixture may comprise one or more separation zones. For example, a MBCAmay comprise only one zone to separate a desired product component fromother impurities when all of those impurities elute either faster orslower than the desired product component. Further as an example, a MBCAmay comprise more than one separation zone, and the components separatedin each zone may have different polarities, or different affinities fora particular stationary phase or particular eluent.

In one aspect, the MBCA is an SMB apparatus. SMB apparatuses suitablefor the separation and purifying a LCDA from a feed mixture may compriseone or more separation zones. For example, a SMB may comprise only onezone to separate a desired product component from other impurities whenall of those impurities elute either faster or slower than the desiredproduct component. Further as an example, a SMB apparatus may comprisemore than one separation zone, and the components separated in each zonemay have different polarities, or different affinities for a particularstationary phase or particular eluent.

In one aspect, the method of the invention comprises a plurality ofzones in a chromatography apparatus, for example, two or more zones canbe used. In another aspect of the present invention there can be 2 to 5zones. Typically, the components separated in each zone of the apparatusused in the method of the present invention have different polarities.The eluent, such aqueous alcohol, containing mixture present in eachzone has a different water:alcohol ratio; and/or the rate at whichliquid collected via the extract and raffinate streams in each zone isrecycled back into the same zone is adjusted such that the LCDA productcan be separated from different components of the feed mixture in eachzone.

When the apparatus used in the method of the present invention has twozones, the present invention typically provides a chromatographicseparation method for recovering a LCDA product, from a feed mixture,which method comprises introducing the feed mixture to a simulated oractual moving bed chromatography apparatus having a plurality of linkedchromatography columns containing, as eluent, an aqueous alcohol,wherein the apparatus has a first zone and a second zone, each zonehaving an extract stream and a raffinate stream from which liquid can becollected from said plurality of linked chromatography columns, andwherein (a) a raffinate stream containing the LCDA product together withmore polar components is collected from a column in the first zone andintroduced to a nonadjacent column in the second zone, and/or (b) anextract stream containing the LCDA product together with less polarcomponents is collected from a column in the second zone and introducedto a nonadjacent column in the first zone, said LCDA product beingseparated from less polar components of the feed mixture in the firstzone, and said LCDA product being separated from more polar componentsof the feed mixture in the second zone.

In an aspect of the present invention, when the apparatus used in themethod contains two zones, the eluent in the first zone contains morealcohol than the eluent in the second zone, and the second zone isdownstream of the first zone with respect to the flow of eluent in thesystem. Thus, the eluent in the system typically moves from the firstzone to the second zone. Conversely, the solid adsorbent phase typicallymoves from the second zone to the first zone. Typically, the two zonesdo not overlap, i.e. there are no chromatographic columns which are inboth zones.

In a further aspect of the invention, the apparatus has a first zone, asecond zone and a third zone. If the eluent is aqueous alcohol, thewater:alcohol ratios of the aqueous alcohol eluent present in the first,second and third zones are typically different. As will be evident toone skilled in the art, this has the consequence that impurities havingdifferent polarities can be removed in each zone.

When the apparatus has three zones, the eluent in the first zone cancontain more alcohol than the eluent in the second zone and the thirdzone and the first zone is upstream of the second and third zones withrespect to the flow of eluent in the system. Typically, the eluent inthe second zone contains more alcohol than the eluent in the third zoneand the second zone is upstream of the third zone with respect to theflow of eluent in the system. Typically, in the first zone, said LCDAproduct is separated from components of the feed mixture which are lesspolar than the LCDA product. Typically, in the second zone, said LCDAproduct is separated from components of the feed mixture which are lesspolar than the LCDA product but more polar than the components separatedin the first zone. Typically, in the third zone, said LCDA product isseparated from components of the feed mixture which are more polar thanthe LCDA product.

Any known simulated or actual moving bed chromatography apparatus may beutilized for the purposes of the method of the present invention, aslong as the apparatus is configured with the multiple, in particulartwo, zones which characterize the method of the present invention. Thoseapparatuses described in U.S. Pat. No. 2,985,589, U.S. Pat. No.3,696,107, U.S. Pat. No. 3,706,812, U.S. Pat. No. 3,761,533,FR-A-2103302, FR-A-2651148, FR-A-2651149, U.S. Pat. No. 6,979,402, U.S.Pat. No. 5,069,883 and U.S. Pat. No. 4,764,276 may all be used ifconfigured in accordance with the method of the present invention.

The number of columns can be 8 or more, for example 15 or more. In oneaspect of the present invention, 15 or 16 columns can be used. Inanother aspect, 19 or 20 columns can be used. In other aspects, 30 ormore columns can be used.

Each zone can consist of an approximately equal share of the totalnumber of columns. For example, in the case of an apparatus configuredwith two zones, each zone typically consists of approximately half ofthe total number of chromatographic columns in the system. The firstzone can comprise 4 or more, for example 8 or more, or about 8 columns.The second zone can comprise 4 or more, for example 7 or more, or about7 or 8 columns.

The dimensions of the columns used in the apparatus will depend on thevolume of feed mixture to be purified. The diameter of each column canbe between 10 mm and 5 m, for example between 5 mm and 500 mm, between25 and 250 mm, between 50 and 100 mm, between 70 and 80 mm, between 0.5m and 5 m, between 1 m and 4 m, or between 2 m and 4 m. The length(i.e., height) of each column can be between 10 cm and 5 m, for examplebetween 10 and 200 cm, between 25 and 150 cm, between 70 and 110 cm,between 80 and 100 cm, between 0.5 m and 5 m, between 1 m and 4 m,between 2 m and 4 m, or between 3 m and 4 m.

The columns in each zone can have identical dimensions but may, forcertain applications, have different dimensions.

The flow rates to the column are limited by maximum pressures across theseries of columns and will depend on the column dimensions and particlesize of the solid phases. Larger diameter columns will in general needhigher flows to maintain linear flow through the columns.

For the typical column sizes outlined above, and for an apparatus havingtwo zones, the flow rate of eluent into the first zone can be from 1 to3,000 L/min, for example from 1 to 4.5 L/min, from 1.5 to 2.5 L/min,from 100 to 2,000 L/min, from 200 to 1,500 L/min, or from 200 to 1,200L/min. The flow rate of the extract from the first zone can be from 0.1to 1,000 L/min, for example from 0.1 to 2.5 L/min, from 0.5 to 2.25L/min, from 100 to 1,000 L/min, from 200 to 1,000 L/min, from 100 to 400L/min, or from 700 to 1,000 L/min. In aspects of the present inventionwhere part of the extract from the first zone can be recycled back intothe first zone, the flow rate of recycle can be for example from 0.7 to600 L/min, from 200 to 600 L/min, from 0.7 to 1.4 L/min, for exampleabout 1 L/min, about 375 L/min, about 80 L/min, or about 320 L/min. Theflow rate of the raffinate from the first zone can be from 0.2 to 3,000L/min, for example from 0.2 to 2.5 L/min, from 0.3 to 2.0 L/min, from100 to 3,000 L/min, from 200 to 3,000 L/min, from 400 to 2,800 L/min,from 300 to 800 L/min, from 2,000 to 3,000 L/min. In aspects where partof the raffinate from the first zone can be recycled back into the firstzone, the flow rate of recycle can be for example from 0.3 to 1,200L/min, from 100 to 1,200 L/min, from 0.3 to 1.0 L/min, for example about0.5 L/min, about 400 L/min, about 70 L/min, or about 350 L/min. The flowrate of introduction of the feed mixture into the first zone can be from5 mL/min to 3,000 L/min, for example from 5 to 150 mL/min, from 10 to100 mL/min, from 20 to 60 mL/min, from 100 to 3,000 L/min, from 200 to2500 L/min, or from 400 to 2500 L/min.

For the typical column sizes outlined above, and for an apparatus havingtwo zones, the flow rate of eluent into the second zone can be from 1 to2,500 L/min, for example from 1 to 4 L/min, from 1.5 to 3.5 L/min, from100 to 2,000 L/min, from 200 to 1,500 L/min, or from 200 to 1,200 L/min.The flow rate of the extract from the second zone can be from 0.5 to 900L/min, for example from 0.5 to 2 L/min, from 0.7 to 1.9 L/min, from 120to 900 L/min, from 200 to 800 L/min, from 100 to 400 L/min, or from 700to 1,000 L/min. In aspects where part of the extract from the secondzone is recycled back into the second zone, the flow rate of recycle canbe for example from 0.6 to 600 L/min, from 200 to 600 L/min, from 0.6 to1.4 L/min, for example from 0.7 to 1.1 L/min, about 0.9 L/min, about 340L/min, about 70 L/min, or about 290 L/min. The flow rate of theraffinate from the second zone can be from 0.5 to 3,000 L/min, forexample from 0.5 to 2.5 L/min, from 0.7 to 1.8 L/min, about 1.4 L/min,from 100 to 3,000 L/min, from 200 to 3,000 L/min, from 400 to 2,800L/min, from 300 to 800 L/min, from 2,000 to 3,000 L/min.

References to rates at which liquid is collected or removed via thevarious extract and raffinate streams refer to volumes of liquid removedin an amount of time, typically L/minute. Similarly, references to ratesat which liquid is recycled back into the same zone, typically to anadjacent column in the same zone, refer to volumes of liquid recycled inan amount of time, typically L/minute.

Part of one or more of the extract stream from the first zone, theraffinate stream from the first zone, the extract stream from the secondzone, and the raffinate stream from the second zone can be recycled backinto the same zone, for example into an adjacent column in the samezone.

This recycle is different from the feeding of an extract or raffinatestream into a non-adjacent column in another zone. Rather, the recycleinvolves feeding part of the extract or raffinate stream out of a zoneback into the same zone, for example into an adjacent column in the samezone.

The rate at which liquid collected via the extract or raffinate streamfrom the first or second zones is recycled back into the same zone cambe the rate at which liquid collected via that stream is fed back intothe same zone, for example into an adjacent column in the same zone.This can be seen with reference to FIG. 9. The rate of recycle ofextract in the first zone is the rate at which extract collected fromthe bottom of column 2 is fed into the top of column 3, i.e. the flowrate of liquid into the top of column 3. The rate of recycle of extractin the second zone is the rate at which extract collected at the bottomof column 10 is fed into the top of column 11, i.e. the flow rate ofliquid into the top of column 11.

Recycle of the extract and/or raffinate streams can be effected byfeeding the liquid collected via that stream into a container, and thenpumping an amount of that liquid from the container back into the samezone. In this case, the rate of recycle of liquid collected via aparticular extract or raffinate stream, for example back into anadjacent column in the same zone, is the rate at which liquid is pumpedout of the container back into the same zone, for example into anadjacent column.

The amount of liquid being introduced into a zone via the eluent andfeedstock streams is balanced with the amount of liquid removed from azone, and recycled back into the same zone. Thus, with reference to FIG.9, for the extract stream, the flow rate of eluent (desorbent) into thefirst or second zone (D) is equal to the rate at which liquid collectedvia the extract stream from that zone accumulates in a container (E1/E2)added to the rate at which extract is recycled back into the same zone(D−E1/D−E2). For the raffinate stream in a zone, the rate at whichextract is recycled back into a zone (D−E1/D−E2) added to the rate atwhich feedstock is introduced into a zone (F/R1) is equal to the rate atwhich liquid collected via the raffinate stream from that zoneaccumulates in a container (R1/R2) added to the rate at which raffinateis recycled back into the same zone (D+F−E1−R1/D+R1−E2−R2).

The rate at which liquid collected from a particular extract orraffinate stream from a zone accumulates in a container can also bethought of as the net rate of removal of that extract or raffinatestream from that zone.

The rate at which liquid collected via the extract stream out of thefirst zone is recycled back into the first zone can differ from the rateat which liquid collected via the extract stream out of the second zoneis recycled back into the second zone, and/or the rate at which liquidcollected via the raffinate stream out of the first zone is recycledback into the first zone can differ from the rate at which liquidcollected via the raffinate stream out of the second zone is recycledback into the second zone.

Varying the rate at which liquid collected via the extract and/orraffinate streams in each zone is recycled back into the same zone hasthe effect of varying the amount of more polar and less polar componentspresent in the other extract and raffinate streams. Thus, for example, alower extract recycle rate results in fewer of the less polar componentsin that zone being carried through to the raffinate stream in that zone.A higher extract recycle rate results in more of the less polarcomponents in that zone being carried through to the raffinate stream inthat zone. This can be seen, for example, in the specific aspect of theinvention shown in FIG. 6. The rate at which liquid collected via theextract stream in the first zone is recycled back into the same zone(D−E1) will affect to what extent any of component A is carried throughto the raffinate stream in the first zone (R1).

The rate at which liquid collected via the extract stream from the firstzone is recycled back into the first zone can be faster than the rate atwhich liquid collected via the extract stream from the second zone isrecycled back into the second zone. In an aspect of the presentinvention, a raffinate stream containing the LCDA product together withmore polar components is collected from a column in the first zone andintroduced to a nonadjacent column in the second zone, and the rate atwhich liquid collected via the extract stream from the first zone isrecycled back into the first zone can be faster than the rate at whichliquid collected via the extract stream from the second zone is recycledback into the second zone.

Alternatively, the rate at which liquid collected via the extract streamfrom the first zone is recycled back into the first zone can be slowerthan the rate at which liquid collected via the extract stream from thesecond zone is recycled back into the second zone.

The rate at which liquid collected via the raffinmate stream from thesecond zone is recycled back into the second zone can be faster than therate at which liquid collected via the raffinate stream from the firstzone is recycled back into the first zone. In an aspect of the presentinvention, an extract stream containing the LCDA product together withless polar components can be collected from a column in the second zoneand introduced to a nonadjacent column in the first zone, and the rateat which liquid collected via the raffinate stream from the second zoneis recycled back into the second zone can be faster than the rate atwhich liquid collected via the raffinate stream from the first zone isrecycled back into the first zone.

Alternatively, the rate at which liquid collected via the raffinatestream from the second zone is recycled back into the second zone can beslower than the rate at which liquid collected via the raffinate streamfrom the first zone is recycled back into the first zone.

The step time, i.e. the time between shifting the points of injection ofthe feed mixture and eluent, and the various take off points of thecollected fractions depends on the number and dimensions of the columnsused, and the flow rate through the apparatus. The step time can be from100 to 1200 seconds, for example from 100 to 1000 seconds, from 200 to800 seconds, or from about 250 to about 750 seconds. In some aspects ofthe present invention, the step time can be from 100 to 400 seconds, orfrom 200 to 300 seconds, or about 250 seconds. In other aspects, thestep time can be from 600 to 900 seconds, or from 700 to 800 seconds, orabout 750 seconds. In other aspects, the step time can be from 400 toabout 800 seconds, from about 500 to 700 seconds, or about 600 seconds.

In one aspect of the method of the present invention, actual moving bedchromatography is used.

Conventional adsorbents for actual and simulated moving bed systems canbe used in the method of the present invention. In some aspects, thestationary phase comprises at least one material selected from the groupconsisting of adsorption resin, activated carbon, floridin, diatomiteand silica gel. In some aspects, the stationary phase is Orpheusnon-polar silica-based stationary phase adsorbent (available fromOrochem Technologies Inc., Naperville, Ill., USA). In some aspects, thestationary phase is C8, C18, or Polar C18 adsorbent (available fromOrochem Technologies Inc., Naperville, Ill., USA).

In some aspects of the present invention, the adsorption resin can bechosen from macroporous adsorption resins. In other aspects, themacroporous adsorption resin can be chosen from nonpolar macroporousadsorption resins for example DOW XAD 418. In yet other aspects, themacroporous adsorption resin can be chosen from polar macroporousadsorption resins. In some aspects, the stationary phase comprisesadsorption resin and at least one material chosen from activated carbon,floridin, diatomite and silica gel.

Each chromatographic column can contain the same or a differentadsorbent. Typically, each column contains the same adsorbent. Examplesof such commonly used materials are polymeric beads, ion exchangeresins, adsorption resin, activated carbon, floridin, diatomite andsilica gel. In one aspect, the adsorbent used in the method of thepresent invention is non-polar.

The shape of the adsorbent stationary phase material can be, forexample, spherical or nonspherical beads. In an aspect of the presentinvention, the stationary phase material can be substantially sphericalbeads. Such beads can have a diameter of from 40 to 500 microns, forexample from 100 to 500 microns, from 250 to 500 microns, from 250 to400 microns, or from 250 to 350 microns. Particle sizes can be somewhatlarger than particle sizes of beads used in the past in simulated andactual moving bed processes. Use of larger particles enables a lowerpressure of eluent to be used in the system. This, in turn, hasadvantages in terms of cost savings, efficiency and lifetime of theapparatus.

The adsorbent can have a pore size of from 6 to 50 nm, for example from15 to 45 nm, from 20 to 40 nm, from 25 to 35 nm, from 6 to 20 nm, from 7to 12 nm, or from 8 to 11 nm.

The eluent used in the method of the present invention is not in asupercritical state. Typically, the eluent is a liquid. The eluent canbe an aqueous alcohol. The aqueous alcohol can comprise water and one ormore short chain alcohols. The short chain alcohol can have from 1 to 6carbon atoms. Examples of suitable alcohols include methanol, ethanol,n-propanol, i-propanol, n-butanol, i-butanol, s-butanol and t-butanol.In some aspects of the present invention, methanol and ethanol can beused. In another aspect, methanol can be used.

The average water:alcohol ratio of the eluent in the entire apparatuscan be from 0.1:99.9 to 95:5 parts by volume, for example from 0.1:99.9to 9:91 parts by volume, from 0.25:99.75 to 7:93 parts by volume, from0.5:99.5 to 6:94 parts by volume, from 5:95 to 20:80 parts by volume,from 50:50 to 95:5 parts by volume, from 30:70 to 70:30 parts by volume,or from 30:70 to 50:50 parts by volume.

The eluting power of the eluent in each of the zones can be different.In an aspect of the present invention, the eluting power of the eluentin the first zone can be greater than that of the eluent in the secondand subsequent zones. In practice this can be achieved by varying therelative amounts of water and alcohol in each zone. Alcohols aregenerally more powerful desorbers than water. Thus, the amount ofalcohol in the eluent in the first zone can be greater than the amountof alcohol in the eluent of the second and subsequent zones.

In aspects of the present invention where the aqueous alcohol present ineach zone has a different water alcohol content, the water:alcohol ratioof the eluent in the first zone can be from 0:100 to 5:95 parts byvolume, for example from 0.1:99.9 to 2.5:97.5 parts by volume, from0.25:99.75 to 2:98 parts by volume, or from 0.5:99.5 to 1.5:98.5 partsby volume. In these aspects, the water:alcohol ratio of the eluent inthe second zone can be from 3:97 to 7:93 parts by volume, from 4:96 to6:94 parts by volume, or from 4.5:95.5 to 5.5:94.5 parts by volume.

In an aspect of the present invention where the aqueous alcohol presentin each zone has a different water alcohol content, the water:alcoholratio of the eluent in the first zone can be from 0.5:99.5 to 1.5:98.5parts by volume, and the water:alcohol ratio of the eluent in the secondzone can be from 4.5:95:5 to 5.5:94.5 parts by volume.

In aspects of the present invention where the rate at which liquidcollected via the extract and raffinate streams in each zone is recycledback into the same zone is adjusted such that the LCDA product can beseparated from different components of the feed mixture in each zone,the water:alcohol ratio of the eluents in each zone can be the same ordifferent. The water:alcohol ratio of the eluent in each zone can befrom 0.5:99.5 to 5.5:94.5 parts by volume. In one aspect, thewater:alcohol ratio of the eluent in the first zone can be lower thanthe water:alcohol ratio of the eluent in the second zone. In anotheraspect, the water:alcohol ratio of the eluent in the first zone can behigher than the water:alcohol ratio of the eluent in the second zone. Ina further aspect, the water:alcohol ratio of the eluent in the firstzone can be the same as the water:alcohol ratio of the eluent in thesecond zone.

The ratios of water and alcohol in each zone referred to above areaverage ratios within the totality of the zone.

The water:alcohol ratio of the eluent in each zone can be controlled byintroducing water and/or alcohol into one or more columns in the zones.Thus, for example, to achieve a lower water:alcohol ratio in the firstzone than in the second zone, water can be introduced more slowly intothe first zone than the second zone. In some aspects of the presentinvention, essentially pure alcohol and essentially pure water can beintroduced at different points in each zone. The relative flow rates ofthese two streams will determine the overall solvent profile across thezone. In other aspects, different alcohol/water mixtures can beintroduced at different points in each zone. That will involveintroducing two or more different alcohol/water mixtures into the zone,each alcohol/water mixture having a different alcohol:water ratio. Therelative flow rates and relative concentrations of the alcohol/watermixtures in this aspect will determine the overall solvent profileacross the zone. In other aspects, where the water:alcohol ratio of theeluent in each zone is the same, the same alcohol/water mixture isintroduced to each zone.

The method of the present invention can be conducted at from 15 to 60°C., for example at from 20 to 40° C., or at about 30° C. Thus, themethod can be carried out at room temperature, but can be conducted atelevated temperatures.

The method of the present invention involves introducing a feed streaminto one zone (for example the first zone), collecting a firstintermediate stream enriched with the LCDA product and introducing thefirst intermediate stream into another zone (for example the secondzone). Thus, when the apparatus has two zones, the method involveseither (a) collecting a first intermediate stream from the first zoneand introducing it into the second zone, or (b) collecting a firstintermediate stream from the second zone and introducing it into thefirst zone. In this way, the LCDA product can be separated from bothmore and less polar components in a single method.

Either (a) a raffinate stream containing the LCDA product together withmore polar components can be collected from a column in the first zoneand introduced to a nonadjacent column in the second zone, or (b) anextract stream containing the LCDA product together with less polarcomponents can be collected from a column in the second zone andintroduced to a nonadjacent column in the first zone.

In one aspect of the present invention, the apparatus has two zones, andthe method comprises: (i) introducing the feed mixture into the firstzone, and removing a first raffinate stream enriched with the LCDAproduct and a first extract stream depleted of the LCDA product, and(ii) introducing the first raffinate stream into the second zone,removing a second raffinate stream depleted of the LCDA product, andcollecting a second extract stream to obtain the LCDA product.

This aspect is illustrated in FIG. 2. A feed mixture F comprising theLCDA product (B) and more polar (C) and less polar (A) components isintroduced into the first zone. In the first zone, the less polarcomponents (A) are removed as extract stream E1. The LCDA product (B)and more polar components (C) are removed as raffinate stream R1.Raffinate stream R1 is then introduced into the second zone. In thesecond zone, the more polar components (C) are removed as raffinatestream R2. The LCDA product (B) is collected as extract stream E2.

This aspect is illustrated in more detail in FIG. 4 and FIG. 4 isidentical to FIG. 2, except that the points of introduction of thealcohol desorbent (D) and water (W) into each zone are shown. Thealcohol desorbent (D) and water (W) together make up the eluent. The (D)phase can be essentially pure alcohol, but may, in certain aspects be analcohol/water mixture comprising mainly alcohol. The (W) phase can beessentially pure water, but may, in certain aspects be an alcohol/watermixture comprising mainly water, for example a 98% water/2% methanolmixture.

A further illustration of this aspect is shown in FIG. 6. Here there isno separate water injection point, and instead an aqueous alcoholdesorbent is injected at (D).

The separation into raffinate and extract stream can be aided by varyingthe desorbing power of the eluent within each zone. This can be achievedby introducing the alcohol (or alcohol rich) component of the eluent andthe water (or water rich) component at different points in each zone.Thus, typically, the alcohol is introduced upstream of the extracttake-off point and the water is introduced between the extract take-offpoint and the point of introduction of the feed into the zone, relativeto the flow of eluent in the system. This is shown in FIG. 4.

Alternatively, the separation can be aided by varying the rates at whichliquid collected via the extract and raffinate streams from the twozones is recycled back into the same zone.

Typically, in this aspect, the rate at which liquid collected via theextract stream from the first zone is recycled back into the first zoneis faster than the rate at which liquid collected via the extract streamfrom the second zone is recycled back into the second zone; or thewater:alcohol ratio of the eluent in the first zone is lower than thatin the second zone.

In this aspect the first raffinate stream in the first zone can beremoved downstream of the point of introduction of the feed mixture intothe first zone, with respect to the flow of eluent in the first zone.

In this aspect, the first extract stream in the first zone can beremoved upstream of the point of introduction of the feed mixture intothe first zone, with respect to the flow of eluent in the first zone.

In this aspect, the second raffinate stream in the second zone can beremoved downstream of the point of introduction of the first raffinatestream into the second zone, with respect to the flow of eluent in thesecond zone.

In this aspect, the second extract stream in the second zone can becollected upstream of the point of introduction of the first raffinatestream into the second zone, with respect to the flow of eluent in thesecond zone.

In this aspect, the alcohol or aqueous alcohol can be introduced intothe first zone upstream of the point of removal of the first extractstream, with respect to the flow of eluent in the first zone.

In this aspect, when water is introduced into the first zone, the watercan be introduced into the first zone upstream of the point ofintroduction of the feed mixture but downstream of the point of removalof the first extract stream, with respect to the flow of eluent in thefirst zone.

In this aspect, the alcohol or aqueous alcohol can be introduced intothe second zone upstream of the point of removal of the second extractstream, with respect to the flow of eluent in the second zone.

In this aspect, when water is introduced into the second zone, the watercan be introduced into the second zone upstream of the point ofintroduction of the first raffinate stream but downstream of the pointof removal of the second extract stream, with respect to the flow ofeluent in the second zone.

In a second aspect of the present invention, the apparatus has twozones, and the method comprises: (i) introducing the feed mixture intothe second zone, and removing a first raffinate stream depleted of theLCDA product and a first extract stream enriched in the LCDA product,and (ii) introducing the first extract stream into the first zone,removing a second extract stream depleted of the LCDA product, andcollecting a second raffinate stream to obtain the LCDA product.

This second aspect is illustrated in FIG. 3. A feed mixture F comprisingthe LCDA product (B) and more polar (C) and less polar (A) components isintroduced into the second zone. In the second zone, the more polarcomponents (C) are removed as raffinate stream R1. The LCDA product (B)and less polar components (A) are collected as extract stream E1.Extract stream E1 is then introduced to the first zone. In the firstzone, the less polar components (A) are removed as extract stream E2.The LCDA product (B) is collected as raffinate stream R2.

This second aspect is illustrated in more detail in FIG. 5 and FIG. 5 isidentical to FIG. 3, except that the points of introduction of the shortchain alcohol desorbent (D) and water (W) into each zone are shown. Asabove, the (D) phase can be essentially pure alcohol, but may, incertain aspects be an alcohol/water mixture comprising mainly alcohol.The (W) phase can be essentially pure water, but may, in certain aspectsbe an alcohol/water mixture comprising mainly water, for example a 98%water/2% methanol mixture.

A further illustration of this second aspect is shown in FIG. 7. Herethere is no separate water injection point, and instead an aqueousalcohol desorbent is injected at (D).

In this second aspect, the rate at which liquid collected via theraffinate stream from the second zone is reintroduced into the secondzone can be faster than the rate at which liquid collected via theraffinate stream from the first zone is reintroduced into the firstzone; or the water:alcohol ratio of the eluent in the first zone can belower than that in the second zone.

In this second aspect, the first raffinate stream in the second zone canbe removed downstream of the point of introduction of the feed mixtureinto the second zone, with respect to the flow of eluent in the secondzone.

In this second aspect, the first extract stream in the second zone canbe collected upstream of the point of introduction of the feed mixtureinto the second zone, with respect to the flow of eluent in the secondzone.

In this second aspect, the second raffinate stream in the first zone canbe collected downstream of the point of introduction of the firstextract stream into the first zone, with respect to the flow of eluentin the first zone.

In this second aspect, the second extract stream in the first zone canbe removed upstream of the point of introduction of the first extractstream into the first zone, with respect to the flow of eluent in thefirst zone.

In this second aspect, the alcohol or aqueous alcohol can be introducedinto the second zone upstream of the point of removal of the firstextract stream, with respect to the flow of eluent in the second zone.

In this second aspect, when water is introduced into the second zone,the water can be introduced into the second zone upstream of the pointof introduction of the feed mixture but downstream of the point ofremoval of the first extract stream, with respect to the flow of eluentin the second zone.

In this second aspect, the alcohol or aqueous alcohol can be introducedinto the first zone upstream of the point of removal of the secondextract stream, with respect to the flow of eluent in the first zone.

In this second aspect, when water is introduced into the first zone, thewater can be introduced into the first zone upstream of the point ofintroduction of the first raffinate stream but downstream of the pointof removal of the second extract stream, with respect to the flow ofeluent in the first zone.

In a third aspect of the present invention, the simulated or actualmoving bed chromatography apparatus consists of fifteen chromatographiccolumns. These are referred to as columns 1 to 15. The fifteen columnsare arranged in series so that the bottom of column 1 is linked to thetop of column 2, the bottom of column 2 is linked to the top of column 3etc. This can optionally be via a holding container, with a recyclestream into the next column. The flow of eluent through the system isfrom column 1 to column 2 to column 3 etc. The flow of adsorbent throughthe system is from column 15 to column 14 to column 13 etc.

In a fourth aspect, the first zone typically consists of eight adjacentcolumns, columns 1 to 8, which are connected as discussed above. In thisfourth aspect, the second zone typically consists of seven columns,columns 9 to 15, which are connected as discussed above. For theavoidance of doubt, the bottom of column 8 in the first zone is linkedto the top of column 9 in the second zone.

In a another aspect, when one or more components exhibit a much strongeraffinity for the stationary phase adsorbent (i.e., much slower runningcomponents) than the other components, the feed containing the LCDA isfirst introduced into a pre-treatment guard bed containing thestationary phase adsorbent to capture the much slower runningcomponents, forming a guard bed effluent of treated feed that is reducedin the much slower running components. The treated feed is subsequentlyintroduced into a SMB unit to separate the LCDA from the other remainingcomponents. In another aspect, two parallel guard beds are employed,where one guard bed is operating to adsorb the much slower runningcomponents in the feed and produce a treated feed, while the other guardbed does not receive a feed and is instead being regenerated byintroducing a desorbent to desorb the much slower running componentsfrom the stationary phase.

In another aspect, the guard bed can be extracted with a solvent toremove the slower running components. If the slower running componentssuch as monocarboxylic acids or hydroxyl acids are unreacted startingmaterial or intermediates in the chemical or biological preparation ofdiacids, the recovered slower running components, after removal ofunwanted solvents, may be recycled back to the chemical or biologicalprocesses.

In another aspect, the extract is fed to an extract desorbent recoverystep to recover desorbent and produce a treated extract that is reducedin desorbent. The specific type of separation step will depend on thephysical properties of the desorbent and other components in theextract. The extract desorbent recovery step can be selection from thenon-limiting group comprising evaporation, distillation,crystallization, vacuum crystallization, and cooling crystallization. Inone aspect, the desorbent that is recovered from the extract desorbentrecovery step is recycled to the SMB unit. In another aspect, thecomponents in the extract such as monocarboxylic acids or hydroxyl acidsare unreacted starting material or intermediates in the preparation ofdiacids may be recycled back to the chemical or biological processes.

In another aspect, the raffinate is fed to a raffinate desorbentrecovery step to recover desorbent and produce a treated raffinate thatis reduced in desorbent. The specific type of separation step willdepend on the physical properties of the desorbent and other componentsin the raffinate. The raffinate desorbent recovery step may comprise onefor more separation unit operations selected from the non-limiting groupcomprising evaporation, distillation, vacuum distillation, filtration,membrane separation, crystallization, evaporative crystallization, andcooling crystallization. In one aspect, the desorbent that is recoveredfrom the raffinate desorbent recovery step is recycled to the SMB unit.

In another aspect, the raffinate is fed to a water removal step toproduce treated raffinate that is reduced in water. The specific type ofwater removal step will depend on the nature of the components in theraffinate. The water removal step may comprise one or more separationunit operations selected from the non-limiting group comprisingevaporation, distillation, vacuum distillation, filtration, membraneseparation, crystallization, evaporative crystallization, and coolingcrystallization. In one aspect the water that is recovered from thewater removal step is recycled to the SMB unit. In one aspect the waterthat is recovered from the water removal step is recycled to afermentation step.

EXAMPLES

The invention is further described in the following examples, which donot limit the scope of the invention described in the claims.

Example 1—HPLC Tests

A 10 μL volume of feed mixture comprising a diacid, a monocarboxylicacid, and a hydroxyl acid in methanol, each at a concentration of 10mg/mL, was injected into an HPLC column containing a stationary phaseadsorbent of 5 μm particle size and 120 Å pore size. An aqueous methanoleluent (i.e., mobile phase) was then fed at a flow rate of 1 mL/min tothe HPLC column (model HP-1100) operating at a set temperature. Theeluent stream leaving the column was analyzed by continuous UV detectionat 220 nm to determine the concentrations and retention times of thediacid, mono carboxylic acid, and hydroxyl acid species.

In examples 1a-1c, the diacid was adipic acid (AA), the monocarboxylicacid was caproic acid (CA), and the hydroxyl acid was 6-hydroxycaproicacid (6-HCA). In examples 1d-1e, the diacid was dodecandioc acid (DDDA),the monocarboxylic acid was lauric acid (LA), and the hydroxyl acid was12-hydroxydodecanoic acid (12-DDA).

Specific feed mixture components, HPLC column dimensions, temperature,stationary phase, aqueous methanol eluent concentration and flow rate,and measured retention times (at peak concentration) of each componentare tabulated in Table 1. Orpheus ADS1, Orpheus ADS2, and Orpheus ADS3are non-polar silica-based stationary phase adsorbents available fromOrochem Technologies Inc., Naperville, Ill., USA. Orpheus ADS2 is morenon-polar than ADS1. Polar C18 non-polar adsorbent (but more polar thannormal C18) is available from Orochem Technologies Inc., Naperville,Ill., USA.

TABLE 1 Eluent HPLC HPLC (Mobile Phase) Eluent Retention Acid ColumnColumn Stationary Methanol: Flow (Elution) Components Diameter ×Temperature, Phase Water Rate, Time, Ex in Feed¹ Length, mm ° C.Adsorbent (vol:vol) mL/min min 1a AA, 6-HCA,   4 × 50 27 Orpheus 50:501.0 AA 2.61; CA ADS1 6-HCA 2.76; CA 9.00 1b AA, 6-HCA,   4 × 50 60Orpheus 11:89 1.0 AA 9.07; CA ADS2 6-HCA 10.43; CA > 60 1e AA, 6-HCA,4.6 × 250 60 Polar  5:95 1.0 AA 12.4; CA C18 6-HCA 14.7; CA > 30 1d DDDA12-   4 × 50 27 Orpheus 70:30 1.0 DDDA 5.52; HDDA, LA ADS1 12-HDDA 6.12;LA 36.27 1e DDDA, 12-   4 × 50 27 Orpheus 63:37 1.0 DDDA 6.40; HDDA, LAADS3 12-HDDA 7.76; LA 35.65

Example 2—Pulse Tests

An aqueous methanol eluent (i.e., mobile phase) of methanol:watervolumetric ratio varying from 95:5 to 80:20 vol:vol was fed at flow rateof 5 mL/min to a column of 10 mm diameter by 250 mm length, packed withOrpheus ADS adsorbent particles of 250-500 μm particle diameter, andmaintained at 60° C. temperature. The mass of the adsorbent wasapproximately 12 g. The eluent flow was temporarily stopped, a 5 mLvolume pulse of feed mixture was injected into the column, the eluentflow was restarted at a flow rate of 5 mL/min, the eluent leaving thecolumn was collected as a series of 5 mL samples every 1 minute, and thesamples were analyzed by mass spectrometer (API 3000 LC-MS/MS) todetermine concentrations of the acid components as a function of timesince feed injection.

In example 2a, the feed mixture composition was 10 wt % AA, 5 wt %6-HCA, and 5 wt % CA in methanol; the adsorbent was OrpheusADS2-equivalent (C18 22% C in FIG. 11; Polar C18 in FIG. 12); and theabsorbance intensity of the eluted components in each collected sampleis plotted in FIGS. 11 and 12. In example 2b the feed mixturecomposition was 10 wt % DDDA, 5 wt % 12-HDDA, and 5 wt % LA in methanol;the adsorbent was Orpheus ADS3-equivalent (C8); and the absorbanceintensity of the eluted components in each collected sample is plottedin FIG. 13.

Example 3—SMB Separation of C6 Diacid

An aqueous feed mixture comprising 10 wt % adipic acid (AA), 0.5 wt %6-hydroxycaproic acid (6-HCA), and 0.5 wt % caproic acid (CA) is fed ata flow rate of 145,874 kg/hr to a SMB unit comprising 15 columns andoperating at 37° C. Each column contains an adsorbent bed 4 m indiameter by 4 m in height of Orpheus ADS2 non-polar silica-basedstationary phase adsorbent of 250 μm particle size and 120 Å pore size,available from Orochem Technologies Inc., Naperville, Ill., USA. Amethanol desorbent (mobile phase) is fed to the SMB unit at a flow rateof 52,083 kg/hr. An extract is withdrawn from the SMB unit at a flowrate of 40,968 kg/hr. A raffinate is withdrawn from the SMB unit at aflow rate of 156,989 kg/hr.

At a time t, the aqueous feed mixture is fed to column 10, the methanoldesorbent is fed to column 1, the extract is withdrawn from column 6,and the raffinate is withdrawn from column 14. Periodically, accordingto a step time, dt, the inlet and outlet flows are each shifted to thenext higher numbered column (i.e., in the direction of liquid flow),simulating an opposite movement of each stationary phase adsorbent bedto the next lower numbered column. Any inlet or outlet flow that waspreviously directed to or from column 15 moves to or from column 1. Inother words, at time t+dt, the aqueous feed mixture is fed to column 11,the methanol desorbent is fed to column 2, the extract is withdrawn fromcolumn 7, and the raffinate is withdrawn from column 15. The total cycletime for the 15-column SMB unit is 15×dt.

The step time, dt, is adjusted to 10 minutes (600 seconds) so that, atsteady-state, the composition of the extract is 1.7 wt % CA, 1.53 wt %6-HCA, 1.7 wt % AA, 3.2 wt % water, and the remainder methanol; thecomposition of the raffinate is 0.02 wt % CA, 0.07 wt % 6-HCA, 8.85 wt %AA, 8.45 wt % methanol, and the remainder water; the AA recovery in theraffinate is 95.2% of the AA in the aqueous feed mixture; and AA purityin the raffinate is 99.0 wt % (on an acids-only basis).

Example 4—SMB Separation of C12 Diacid

An aqueous feed mixture comprising 10 wt % dodecandioic acid (DDDA), 0.5wt % 12-hydroxydecanoic acid (12-HDDA), and 0.5 wt % lauric acid (LA) isfed at a flow rate of 29,167 kg/hr to a SMB unit comprising 15 columnsand operating at 37° C. Each column contains an adsorbent bed 2 m indiameter by 3 m in height of Orpheus ADS3 non-polar silica-basedstationary phase adsorbent of 250 μm particle size and 120 Å pore size,available from Orochem Technologies Inc., Naperville, Ill., USA. Amethanol desorbent (mobile phase) is fed to the SMB unit at a flow rateof 12,188 kg/hr. An extract is withdrawn from the SMB unit at a flowrate of 10,034 kg/hr. A raffinate is withdrawn from the SMB unit at aflow rate of 31,320 kg/hr.

At a time t, the aqueous feed mixture is fed to column 10, the methanoldesorbent is fed to column 1, the extract is withdrawn from column 6,and the raffinate is withdrawn from column 14. Periodically, accordingto a step time, dt, the inlet and outlet flows are each shifted to thenext higher numbered column (i.e., in the direction of liquid flow),simulating an opposite movement of each stationary phase adsorbent bedto the next lower numbered column. Any inlet or outlet flow that waspreviously directed to or from column 15 moves to or from column 1. Inother words, at time t+dt, the aqueous feed mixture is fed to column 11,the methanol desorbent is fed to column 2, the extract is withdrawn fromcolumn 7, and the raffinate is withdrawn from column 15. The total cycletime for the 15-column SMB unit is 15×dt.

The step time, dt, is adjusted so that, at steady-state, the compositionof the extract is 1.5 wt % LA, 1.3 wt % 12-HDDA, 1.4 wt % DDDA, 0.3 wt %water, and the remainder methanol; the composition of the raffinate is 0wt % LA, 0.04 wt % 12-HDDA, 8.85 wt % DDDA, 8.28 wt % methanol, and theremainder water; the DDDA recovery in the raffinate is 95.2% of the DDDAin the aqueous feed mixture; and the DDDA purity in the raffinate is99.5 wt % (on an acids-only basis).

1. A method for separating a C6- to C18-carbon diacid from at least oneimpurity in a solution, comprising: (a) introducing a feed streamcomprising a solution comprising at least one 6- to 18-carbon diacid andat least one impurity, the at least one impurity comprising a componentmore polar than the diacid, a component less polar than the diacid, orboth, into a first zone of moving bed chromatography apparatus (MBCA)having one or more zones; (b) collecting a raffinate stream or anextract stream from the first zone of the MBCA, the raffinate streamcomprising the diacid and one or more components more polar than thediacid, and the extract stream comprising the diacid and one or morecomponents less polar than the diacid; (c) introducing the raffinatestream or the extract stream into a second zone of the MBCA; (d)collecting a second raffinate stream or a second extract stream from thesecond zone of the MBCA, the raffinate stream comprising the diacid andcomponents more polar than the diacid, and the extract stream comprisingthe diacid and components less polar than the diacid; (e) introducingthe second raffinate stream or the second extract stream into the firstzone or the second zone of the MBCA; (f) optionally repeating steps (d)and (e) until a desired degree of separation is achieved; and (g)collecting a final raffinate stream or a final extract stream from azone of the MBCA, the final raffinate stream or the extract streamcomprising the diacid, thereby separating a C6- to C18-carbon diacidfrom the at least one impurity in the solution.
 2. A method forseparating a C6- to C18-carbon diacid from at least one impurity in asolution, comprising: (a) introducing a feed stream comprising asolution comprising at least one 6- to 18-carbon diacid and at least oneimpurity, the at least one impurity comprising a component more polarthan the diacid, a component less polar than the diacid, or both, into afirst zone of a moving bed chromatography apparatus (MBCA); (b)collecting a raffinate stream or an extract stream from the MBCA, theraffinate stream comprising the diacid and components more polar thanthe diacid, and the extract stream comprising the diacid and componentsless polar than the diacid; (c) introducing the raffinate stream or theextract stream into the first zone of the MBCA; (d) optionally repeatingsteps (b) and (c) until a desired degree of separation is achieved; and(e) collecting a final raffinate stream or a final extract stream fromthe first zone of the MBCA, the final raffinate stream or the extractstream comprising the diacid, thereby separating a C6- to C18-carbondiacid from the solution.
 3. The method of claim 1, wherein the at leastone impurity is present in a final raffinate stream or a final extractstream at about 10,000 ppmw or less, about 5,000 ppmw or less, about1,000 ppmw or less, about 500 ppmw or less, about 100 ppmw or less,about 50 ppmw or less, or about 10 ppmw or less.
 4. The method of claim1, further comprising introducing the raffinate stream or the extractstream into first zone of the MBCA prior to first raffinate stream orthe first extract stream introducing the raffinate stream or the extractstream into a second zone of the MBCA.
 5. The method of claim 1,wherein: the MBCA comprising two or more zones, each zone comprising oneor more injection points for introducing the solution; one or moreinjection points for introducing an eluent; a raffinate stream fromwhich liquid can be collected; and an extract stream from which liquidcan be collected.
 6. The method of claim 1, wherein the at least oneimpurity is: (a) a monocarboxylic acid, an alkane, or a hydroxyl acid;(b) more polar than the 6- to 18-carbon diacid; or (c) less polar thanthe 6- to 18-carbon diacid.
 7. (canceled)
 8. (canceled)
 9. The method ofclaim 1, wherein the at least one 6- to 18-carbon diacid is: (a) an α,or ω diacid; (b) an alkane diacid or an olefin diacid; or (c) selectedfrom a C6 diacid (adipic acid), C7 diacid (pimelic acid), C8 diacid(suberic), C9 diacid (azelaic acid), C10 diacid (sebacic acid), C11diacid (undecanedioic acid), C12 diacid (dodecanedioic acid), C13 diacid(tridecanedioic acid), C14 diacid (tetradecanedioic acid), C15 diacid(pentadecanedioic acid), C16 diacid (hexadecanedioic acid), C17 diacid,(heptadecanedioic acid) C18 diacid (octadecanedioic acid), andC6-18-olefin diacid.
 10. (canceled)
 11. (canceled)
 12. The method ofclaim 1, wherein the at least one 6- to 18-carbon diacid is: (a)produced by chemical means; (b) comprises a fermentation broth from abiological mixture; or (c) is a bioderived compound produced byfermentation.
 13. (canceled)
 14. (canceled)
 15. The method of claim 1,wherein the MBCA comprises: (a) three to fifteen chromatography columns;(b) two or more zones; (c) two zones, the eluent in the first zonecontaining more alcohol than the eluent in the second zone, and thesecond zone being downstream of the first zone with respect to the flowof eluent in the system; or (d) a first zone, a second zone, and a thirdzone, the eluent in the first zone containing more alcohol than theeluent in the second zone and the third zone and the first zone beingupstream of the second and third zones with respect to the flow ofeluent in the system, and the eluent in the second zone containing morealcohol than the eluent in the third zone and the second zone beingupstream of the third zone with respect to the flow of eluent in thesystem. 16-18. (canceled)
 19. The method of claim 1, wherein the eluentcomprises an aqueous alcohol.
 20. The method of claim 1, wherein the C6-to C18-carbon diacid recovery is at least 80%, 82%, 85%, 88%, 90%, 91%,92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or at least 99.9% relative tothe amount of the at least one impurity.
 21. A method for obtaining adiacid comprising: (a) providing a solution comprising at least one C6-to C18-carbon diacid and at least one impurity; (b) introducing thesolution into a moving bed chromatography apparatus (MBCA) having one ormore chromatography columns and at least one eluent; (c) producing araffinate and an extract; (d) recovering a purified C6- to C18-carbondiacid composition from the raffinate or the extract, or both, whereinsaid at least one impurity is present in the purified diacid compositionat about 10,000 ppmw or less, about 5,000 ppmw or less, about 1,000 ppmwor less, about 500 ppmw or less, about 100 ppmw or less, about 50 ppmwor less, or about 10 ppmw or less.
 22. The method of claim 21, whereinthe C6- to C18-carbon diacid recovery is at least 80%, 82%, 85%, 88%,90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or at least 99.9%relative to the amount of the at least one impurity.
 23. The method ofclaim 1, comprising: (a) introducing a feed stream comprising a solutioncomprising adipic acid, 6-hydroxycaproic acid, and caproic acid, into afirst zone of moving bed chromatography apparatus (MBCA); (b) collectinga raffinate stream or an extract stream from the first zone of the MBCA,the raffinate stream comprising the adipic acid and 6-hydroxycaproicacid, and the extract stream comprising the adipic acid and caproicacid; (c) introducing the raffinate stream or the extract stream into asecond zone of the MBCA; (d) collecting a second raffinate stream or asecond extract stream from the second zone of the MBCA, the raffinatestream comprising the adipic acid and 6-hydroxycaproic acid, and theextract stream comprising the adipic acid and caproic acid; (e)introducing the second raffinate stream or the second extract streaminto the first zone or the second zone of the MBCA; (f) optionallyrepeating steps (d) and (e) until a desired degree of separation isachieved; and (g) collecting a final raffinate stream or a final extractstream from a zone of the MBCA, the final raffinate stream or theextract stream comprising the adipic acid, thereby separating the adipicacid from the 6-hydroxycaproic acid and caproic acid.
 24. The method ofclaim 1, comprising: (a) introducing a feed stream comprising a solutioncomprising dodecanedioic acid, 12-hydroxydecanoic acid and lauric acid,into a first zone of moving bed chromatography apparatus (MBCA); (b)collecting a raffinate stream or an extract stream from the first zoneof the MBCA, the raffinate stream comprising the dodecanedioic acid and12-hydroxydecanoic acid, and the extract stream comprising thedodecanedioic acid and lauric acid; (c) introducing the raffinate streamor the extract stream into a second zone of the MBCA; (d) collecting asecond raffinate stream or a second extract stream from the second zoneof the MBCA, the raffinate stream comprising the dodecanedioic acid and12-hydroxydecanoic acid, and the extract stream comprising thedodecanedioic acid and lauric acid; (e) introducing the second raffinatestream or the second extract stream into the first zone or the secondzone of the MBCA; (f) optionally repeating steps (d) and (e) until adesired degree of separation is achieved; and (g) collecting a finalraffinate stream or a final extract stream from a zone of the MBCA, thefinal raffinate stream or the extract stream comprising thedodecanedioic acid, thereby separating the dodecanedioic acid from the12-hydroxydecanoic acid and lauric acid.
 25. (canceled)
 26. A moving bedchromatography apparatus (MBCA) for separating a C6- to C18-carbondiacid from at least one impurity in a solution, comprising: (a) a firstzone configured to receive a feed stream comprising a solutioncomprising at least one 6- to 18-carbon diacid and at least oneimpurity, the at least one impurity comprising a component more polarthan the diacid, a component less polar than the diacid, or both; (b)the first zone configured to produce a raffinate stream or an extractstream from the MBCA, the raffinate stream comprising the diacid andcomponents more polar than the diacid, and the extract stream comprisingthe diacid and components less polar than the diacid; (c) a second zoneconfigured to receive the raffinate stream or the extract streamproduced from the first zone; (d) the second zone configured to producea raffinate stream or an extract stream from the MBCA, the raffinatestream comprising the diacid and components more polar than the diacid,and the extract stream comprising the diacid and components less polarthan the diacid; (e) the MBCA configured to allow the raffinate streamor extract stream from said second zone to be reintroduced into thefirst zone or the second zone of the MBCA until a desired degree ofseparation is achieved to produce a final raffinate stream or a finalextract stream from a zone the MBCA, the final raffinate stream or theextract stream comprising the diacid, thereby separating a C6- toC18-carbon diacid from the solution. 27-29. (canceled)